1. Field of the Invention
The present invention relates to a golf club. In more detail, it relates to a golf club which is improved by arranging a weight, chiefly in the crown section, in order to improve carry.
2. Description of the Related Art
Usually, when teeing off, a golf club called a “driver” is employed in order to achieve a long carry. The carry directly influences the score, so conditions at the impact point on the head of the golf club represent a vital factor. Although the face section i.e. the striking surface is the most important factor, the loft angle is also a factor which cannot be neglected in achieving carry.
In general, if the loft angle is small, the ball flies in a condition closer to the horizontal and a long carry is not usually obtained. On the other hand, if the loft angle is large, the ball flies upwards and in this case also a long carry is not obtained. As described above, the optimum loft angle is set for each club on the basis of experience, though it is also affected by the coefficient of restitution at the position of impact on the face section. Typically, the loft angle is about 11°. The angle of launching of the trajectory of the ball that is struck increases as the loft angle is made larger and, even in this condition, ideally, the golf club should be such as to easily hit the ball in a manner that decreases the amount of backspin.
In order to achieve this, golf clubs are known of a construction facilitating flexing by making the crown section of another material, but they are liable to the formation of cracks. Thus there are various problems concerning golf clubs and various studies have been made. For example, Laid-open Japanese Patent Application No. 11-333037 proposes a golf club in which a weight is disposed at the crown section and the face section, but this does not guarantee an optimum relationship of the speed of backspin rotation and carry. The factors that give a golf ball a long carry are basically three: namely, increasing the initial speed of the ball, the correct amount of backspin, and the correct launching angle. Of these, the coefficient of restitution (C. O. R.) of the face section may be raised in order to increase the initial speed of the ball, but a limit on the coefficient of restitution is imposed by the rules.
On the other hand, the amount of backspin and the launching angle are mutually opposing factors. Ideally, the launching angle is fairly large and the amount of backspin is small, so for example backspin of about 2000 to 3000 rpm is suitable. Even more preferably, the amount of backspin should be as close as possible to 2000 rpm. However, although, in order to obtain a large launching angle, the loft angle suitably tends to be large, as described above, this increases the amount of backspin, giving rise to the problem that the ball rises and hence does not travel far.
As described above, expedients have been adopted in order to increase the carry under various conditions, but the problems have not necessarily been satisfactorily solved. Whereas there are restrictions on increasing the coefficient of restitution in order to achieve a good golf strike, and although, conventionally, the loft angle was increased in order to increase the launching angle, the ideal would be to employ a golf club capable of achieving a long carry by reducing the amount of backspin.
Development of a golf club is therefore desired which, without differing greatly from the conventional shape and without restricting function, should be close to the ideal condition described above, enabling the carry to be extended in a stable fashion.